June 2006 - Boost-users - lists.preview.boost.org

boost::pool
by James Swift 06 Jun '06

06 Jun '06

Hi boost users, I have a question regarding the best use of the boost pools and shared_ptr Consider the following tree node object. class A { public: typedef boost::shared_ptr< A > SPA; typedef std::vector< SPA > SPAVec; SPAVec children; }; This class allows me to have a tree or trees where some of the nodes may be shared. E.g. // tree1 tree2 // X Z // Y Y Y X // Y Y Logically the root of tree1, X has two children Y and Y but physically of course I only have one copy of Y in memory. Other trees, e.g. tree2 can also share these branches. Now assume I'm also very often constructing and destroying nodes. An object pool is an obvious optimisation to try out. However shared_ptr would need to call object_pool::destruct() instead of delete when it really wants to destroy the object. Or singleton_pool::free() but this causes more difficulties for me because I want to control the lifetime of the pool separately for each instance of my objects which are working on these trees. Can anyone offer a nice solution to this problem? kind regards, James Swift.

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random library: initializaing a generator.
by dvir schirman 06 Jun '06

06 Jun '06

Hi I am using boost/random library in order to create a normal distributed noise. I want to call my my_class::noise() functions several times, but I want to initialize the generator only once. I tried to declare and initialize the generator at the constructor of my_class, but then my_class::noise() doesn't recognized the generator. I wrote it the following way: my_class::my_class() { boost::mt19937 gen(42u); } my_class::noise() { boost::normal_distribution<float> n_d(5, 10); //n_d(mean,stdev) boost::variate_generator<boost::mt19937&, boost::normal_distribution<float> > normal(gen, n_d); return normal(); } I guess I need to declare the generator at the header, and only initialize it at the constructor, but I don't know how to do it. Thanks for your help. Dvir

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Re: [Boost-users] random library: initializaing a generator.
by David Klein 06 Jun '06

06 Jun '06

boost-users-bounces(a)lists.boost.org wrote: > Hi > > I am using boost/random library in order to create a normal > distributed noise. I want to call my my_class::noise() functions > several times, > but I want to initialize the generator only once. > I tried to declare and initialize the generator at the > constructor of my_class, but then my_class::noise() doesn't > recognized the generator. I wrote it the following way: > > my_class::my_class() > { > boost::mt19937 gen(42u); > > } > > my_class::noise() > > { > > boost::normal_distribution< > > float> n_d(5, 10); //n_d(mean,stdev) > > boost::variate_generator<boost::mt19937&, > boost::normal_distribution<float> > normal(gen, n_d); > > return normal(); > > } > > > > I guess I need to declare the generator at the header, and > only initialize it at the constructor, but I don't know how to do it. > > Thanks for your help. > Dvir hi dvir, this is untested, but should do what you want. class my_class { boost::mt19937 gen_; public: my_class( void ) : gen_(42u) { } void noise( void ) { boost::normal_distribution<float> n_d(5, 10); //n_d(mean,stdev) boost::variate_generator<boost::mt19937&, boost::normal_distribution<float> > normal(gen_, n_d); } }; HTH dave

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[multi_index].[composite_key] Index creation at run-time.
by Prashant Thakre 06 Jun '06

06 Jun '06

Hi, I would like to know if it's possible to define a multi_index using composite_key,where the number of keys which are part of the composite_key are only known at run-time. Thanks again. -- regards, Prashant Thakre

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[Test] Can Boost Test Tools Be Used in Multiple Threads?
by Wu Yinghui, Freddie 05 Jun '06

05 Jun '06

Dear all, I've been trying to write some test code that involves 2 concurrent threads of execution. But I found that there are occasional crashes in the test tool code when some BOOST_CHECK_*() are triggered. So my question is: Are Boost test tools designed to be used in multiple threads? Cheers, Freddie -- Wu Yinghui, Freddie Research & Development Software Engineer Volume Interactions Pte Ltd 1 Kim Seng Promenade, #12-01 Great World City East Tower Singapore 237994 Tel: +65 62226962 (Ext 216) Fax: +65 62226215 Email: yhwu(a)volumeinteractions.com URL: http://www.volumeinteractions.com Important: This message is intended for the recipient(s) addressed above. It contains privileged and confidential information. If you are not the intended recipient, please notify the sender immediately by replying to this message and then delete it from your system. You must not read, copy, use, or disseminate this communication in any form. Thank you.

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[serialization] boost::archive::archive_exception expected on invalid contents on GNU/Linux
by Julien Pervillé 05 Jun '06

05 Jun '06

Hello boost-users! I would like to report a minor (but annoying) bug in the boost::serialization library which I am using extensively in my project. The problem: trying to load serialized data from a known invalid archive does not throw a boost::archive::archive_exception but instead a normal std::exception is caught. Note: the bug seems to only affect GNU/Linux systems. The annoyance is minor since some kind of exception is caught anyway so that corrective action can be taken. At some point in my application's test suite, I test the robustness of my persistence code by feeding my Load() method a malformed buffer. If I run the test suite normally I get the expected result that is an exception happened and the program refused to corrupt its internal data structure. However, when running under Valgrind looking for leakage, I get spammed by "Conditional jump or move depends on uninitialised value(s)" messages. It appears that boost::serialization does not notice that my source stream is a malformed archive and recklessly tries to read the serialized data. As I can see in the many "load" methods from "boost/archive/impl/text_iarchive_impl.ipp" (the last method invoked before the exception occurs), the archive loader attempted to read a "size" from the malformed data and then attempted to resize its buffer to this (undefined) size, ensuing mayhem. Aren't the archive loaders supposed to check that a stream is a valid archive before deserializing? I would imagine that the boost::archive::archive_exception::invalid_archive error code is made for that purpose. Here are instructions on how to trigger the bug: a very simple boost::serialization example and the valgrind trace (compiled with -g). Here is a sample execution of the program: jp@linux ~/boost $ ./malformed-contents caught exception : basic_string::resize The compiler used was g++-4.1 on GNU/Linux (amd athlon, gentoo distribution, glibc 2.3.6). I reproduced the issue on another GNU/Linux box with an AMD 64 and g++ 3.4 and obtained the same issue. However, running the test on my ibook (Apple OSX) returned me the expected behavior : ibook:~/boost jp$ ./malformed-contents caught boost exception : invalid signature The issue seems to only affect some GNU/Linux systems. Thank you for the help, Sincerely, Julien Pervillé Intern, Global Core, Amadeus IT Group.

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[statechart ] UML2.0 local transitions and history
by Tim Milward 05 Jun '06

05 Jun '06

I've built a small test program with the statechart library. (See below) It seems that the sequence of exit and entry actions invoked for a transition are modeled according to the UML 1.5 specification. In other words it models "external" transitions from the 2.0 spec. Is it possible, or are there any plans to extend it, to model the more useful local transitions from the 2.0 spec? Tests with deep history produce a static assertion if you attempt to transition to history of a containing state. UML 2.0 explicitly permits this. Are there any plans to modify the library to permit this? Yours, Tim Milward #include <iostream> #include <boost/statechart/event.hpp> #include <boost/statechart/state_machine.hpp> #include <boost/statechart/simple_state.hpp> #include <boost/statechart/transition.hpp> #include <boost/statechart/deep_history.hpp> using namespace std; namespace sc = boost::statechart; struct S0; struct S00; struct Machine : sc::state_machine< Machine, S0 > { Machine() { cout << "Machine()\n"; } ~Machine() { cout << "~Machine()\n"; } }; struct E0 : sc::event< E0 > { E0() { cout << "E0()\n"; } ~E0() { cout << "~E0()\n"; } }; struct E1 : sc::event< E1 > { E1() { cout << "E1()\n"; } ~E1() { cout << "~E1()\n"; } }; struct S0 : sc::simple_state< S0, Machine, S00, sc::has_deep_history > { // this would comile fine // typedef sc::transition<E0, sc::deep_history< S00 > > reactions; // this invokes exit actions of S00 and S0 (an external transition) typedef sc::transition<E0, S00 > reactions; S0() { cout << "S0()\n"; } virtual ~S0() { cout << "~S0()\n"; } }; struct S00 : sc::simple_state< S00, S0 > { // this doesn't compile // typedef sc::transition<E1, sc::deep_history< S00 > > reactions; // this invokes exit actions of S00 only typedef sc::transition<E1, S00 > reactions; S00() { cout << "S00()\n"; } virtual ~S00() { cout << "~S00()\n"; } }; int main() { Machine m; m.initiate(); m.process_event(E0()); m.process_event(E1()); return 1; }

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[review] Fusion Library Accepted
by Ronald Garcia 05 Jun '06

05 Jun '06

Dear All, I am pleased to announce that the Fusion compile-time/run-time hybrid heterogeneous container and algorithm library by Joel de Guzman and Dan Marsden has been accepted into Boost. The library received 7 YES votes and 0 NO votes, with one abstention. Detailed Review Comments ------------------------ The following comments refer to issues that the library authors should address prior to merging the library into CVS: * Documentation: Many of the reviewers stated that they would like to see more tutorial documentation that demonstrates not only what the particular constructs in Fusion do, but also how they are expected to be used. A reasonably concise motivating example has been requested. It has already been pointed out that Fusion is used for some other boost libraries. A well-developed and self-contained case study of when and how to use Fusion would be greatly appreciated. The relationship between this library and the current Boost.Tuple library, as well as Boost.Mpl, should be discussed. The reference documentation is quite thorough and detailed comments regarding them have already been addressed by the authors. However the notion of "views" requires greater documentation. The examples in the algorithm sections currently do little more than demonstrate the syntax by which they can be called. Examples that more specifically express intent would be a notable improvement. (see for example Matt Austern's "Generic Programming and the STL"). In general the documentation would benefit from copy-editing. * Several commented on the use of the name "pair" for the fusion type that has typedefs for two types but only contains the second type. Although the typedefs and member names are consistent with the std::pair object, the name "pair" is confusing. The compile-time/run-time hybrid nature of this library makes it difficult to find perfect metaphors for constructs in the library. In this case, it seems better to find a term for this template (and the concept that it models) that more directly states its purpose. The name "tag_of" would also benefit from renaming. * The behavior of Fusion functions in the face of argument-dependent lookup (ADL) is not well specified. This should be made explicit in the reference documentation. The following comments refer to issues that, while not mandatory, deserve consideration: * The library name "Fusion", though not arbitrary, says little about the library's purpose. There is precedent for this within boost, however. A name change is not mandatory for the library's acceptance, but it would be worth while for the authors to consider a more telling name. * The mechanism for extending Fusion with new containers and iterators is complex and involves implementing a number of components, especially regarding iterators. An adaptation layer that is analogous to the Boost.Iterator library would be a fine addition to Fusion. * It would be beneficial to supply Boost.Serialization support for the Fusion container types. I am sure, as mentioned, that the authors of this library would accept a volunteer to implement this functionality. I would like to thank all the people who reviewed the library, voted, and otherwise participated in the discussion. Congratulations to Joel and Dan and I look forward to seeing Fusion in the Boost CVS soon. Ron Garcia

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[BJAM / BGL] build error: no builtin module .ENVIRON is found
by John Reid 05 Jun '06

05 Jun '06

Hi, I'm trying to compile the boost graph library python bindings. They need Boost.Jam version 3.1.12 which I have downloaded and built from CVS. However when I run bjam I get the following error: error: no builtin module .ENVIRON is found error: your version of bjam is likely out of date error: please get a fresh version from CVS. Can anyone tell me what I'm doing wrong? Perhaps this is a problem with the BGL Jamfiles? Thanks, John.

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shmem and mingw 3.4.4 and visual c++ 7.0
by Jan Stetka 04 Jun '06

04 Jun '06

Hi, MinGW gcc 3.4.4 is an important compiler to be supported for those keeping up the open source effort on windows. Below are a couple compilation problems and solutions in case Ion doesn't find time to fix them. Compiling shmem with Visual C++ 7.0 gives a number of errors, for those interested who could maybe suggest workarounds: http://myweb.tiscali.co.uk/janstetka/Output-Build.txt Compiling shmem with MinGW gcc 3.4.4 it appears that the following headers are required #include <boost/shared_ptr.hpp> #include "boost/shmem/offset_ptr.hpp" before shmem/containers/map.hpp and #include <stdarg.h> before #include "boost/shmem/sync/xtime.hpp" and MinGW gcc 3.4.4 doesn't like a number assigned to a variable in xtime.hpp c:/boost_1_33_1/boost/shmem/sync/xtime.hpp: In function `int boost::shmem::xtime_get(boost::shmem::xtime*, int)': c:/boost_1_33_1/boost/shmem/sync/xtime.hpp:89: error: integer constant is too large for "long" type this refers to the following code: static const boost::uint64_t timespec_to_filetime_offset = (boost::uint64_t)(116444736000000000); if this is altered to: static const boost::uint64_t timespec_to_filetime_offset = (boost::uint64_t)(116444736000000000ULL); then it compiles. Thanks

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